Mislabeling and nomenclatorial confusion of Typhlotanais sandersi Kudinova-Pasternak, 1985 (Crustacea: Tanaidacea) and establishment of a new genus

Re-examination of historical collections allowed us to resolve the taxonomic status of Typhlotanais sandersi Kudinova-Pasternak, 1985, originally described based on a single specimen from Great-Meteor Seamount. The holotype of this species was considered lost and the species redescribed based on a second specimen from the type locality by Błażewicz-Paszkowycz (2007a), who placed Ty. sandersi on a newly established genus Typhlamia. Thorough morphological analysis of Typhlamia and Typhlotanais species and recently obtained genetic data of typhlotanaids from N Atlantic and NW Pacific waters allow us to conclude that the redescription of Ty. sandersi by Błażewicz-Paszkowycz (2007a) was based on a wrongly labelled specimen that, rather than a type of Ty. sandersi, represents in fact a new species of Typhlamia. The morphological comparison of the type species of Typhlotanais (Ty. aequiremis) with all ‘long-bodied’ typhlotanaid taxa with rounded pereonites margins (i.e., Typhlamia, Pulcherella, Torquella), and the use of genetic evidence, support the establishment of a new genus to accommodate: Ty. sandersi, Ty. angusticheles Kudinova-Pasternak, 1989, and a third species from N Atlantic waters, that is described here for the first time. Current knowledge on ‘long-bodied’ typhlotanaids with rounded pereonites is summarised and a taxonomical key for their identification provided.

After a new species of Typhlamia Błażewicz-Paszkowycz, 2007a was collected from Northwest Pacific waters (Gellert, Palero & Błażewicz, 2022), detailed morphological analysis and literature revision has revealed that the original description of Ty. sandersi by Kudinova-Pasternak (1985) differed from the redescription made by Błażewicz-Paszkowycz (2007a). A thorough morphological analysis of 'long-bodied' typhlotanaids with rounded pereonite margins (e.g., Typhlamia, Pulcherella, Torquella), all different from Ty. aequiremis, has allowed us to conclude that the putative Ty. sandersi specimen studied by Błażewicz-Paszkowycz (2007a) was wrongly labelled and in fact represents a different species and genus from the Ty. sandersi described and figured by Kudinova-Pasternak (1985). This article aims to correct the taxonomic mixing of Ty. sandersi described by Kudinova-Pasternak (1985) and Tm. sandersi sensu Błażewicz-Paszkowycz (2007a) and to establish a new genus with the support of additional morphological and molecular evidence.
As a result of morphological analysis of long body typhlotanaids with rounded pereonite margins, a new morphological group 'variabilis' was distinguished, for which the definition is given here for the first time.

Genetic analyses
All sequences used in the molecular studies are from GenBank. Sequences from Gellert, Palero & Błażewicz (2022) were obtained from the University of Lodz Tanaidacea collection (GenBank accession numbers: ON310832-ON310845 for COI and ON255540-ON255555 for 18S rDNA; see Table 2). The molecular tree used in the current study come from publication by Gellert, Palero & Błażewicz (2022

TERMINOLOGY AND SPECIES DESCRIPTION
Total body length (BL) was measured along the central axis of symmetry from the frontal margin to the end of pleotelson; body width (BW) was measured perpendicular to the main axis at the widest point of pereonite-3. Width and length of carapace, pereonites, pleonites, and pleotelson were measured on whole specimens. All measurements were taken using a digital camera connected to the microscope (Nikon Eclipse Ci-L) and the NIS-Elements View software (www.nikoninstruments.com). The clinging apparatus is a system of various hooks, tubercles, thorns, and spines located on the carpus of pereopods 4−6 (Błażewicz-Paszkowycz, 2007a;. Unspecified setae in taxonomic descriptions are referred here as simple setae (= without ornamentation) by default. Besides, we recognize penicillate setae-with a distal tuft of setules and supracuticular articulation, and rod setae-distally inflated seta and with a terminal pore (Thomas, 1970;Garm, 2004). The short ventral seta situated besides two long setae on the cheliped carpus is called 'third' seta. The distal part of the cheliped basis, extending backwards, is referred here as 'cheliped lobe' (Larsen, 2005). The term 'collar' is used to refer the shape of pereonite-1, with a deeply concave anterior edge and lateral corners extended forwards (e.g., Torquella Błażewicz-Paszkowycz, 2007a). Błażewicz-Paszkowycz (2007a) proposed a classification of typhlotanaids into 'short-bodied' (body <6.0 L:W) and 'long-bodied' (body ≥8.0 L:W) taxa (see the Key for Typhlotanaidae genera and morpho-groups in Błażewicz-Paszkowycz, 2007a). The neuter is the post-manca stage, that cannot be classified as male or female. Two-letter genus abbreviations are used throughout the text to distinguish between genera: Tq. = Torquella, Tm. = Typhlamia and Ty. = Typhlotanais. Type material for the species described here is deposited in the Museum der Natur Hamburg, Germany (ZMHK) and ICUL/ITan numbers correspond to unique identifiers from the Invertebrates Collection held at the University of Lodz, Poland.

RESULTS AND INTERPRETATION
The recent discovery of a new species of Typhlamia from the Kuril-Kamchatka Trench (Gellert, Palero & Błażewicz, 2022) and the re-evaluation of Typhlotanais sp. A from Błażewicz-Paszkowycz et al. (2014) uncovered significant genetic and morphological differences between Typhlamia and the morphogroup of species including the original holotype description and drawings of Typhlotanais sandersi Kudinova-Pasternak, 1985.
Although types of all taxa described by Kudinova-Pasternak were deposited at the Zoological Museum in Moscow after her retirement (R.K. Kudinova-Pasternak in 2004, personal communication), all microscopic slides made for studying and illustrating morphological details were disposed of, even those with holotype appendages. For this reason, most of the type collection studied by Kudinova-Pasternak (except undissected type material) should be considered lost. This situation is particularly critical for Ty. sandersi Kudinova-Pasternak (1985), of which a single specimen was dissected after the habitus was illustrated.
According to Kudinova-Pasternak (1985), two Typhlotanais specimens were collected from the same station (st. 162) during the RV Vitjaz expedition at the base of the Great-Meteor Seamount: the holotype of Ty. sandersi described and drawn in the text and another individual identified as Typhlotanais mucronatus Hansen, 1913 (currently Typhlamia mucronata (Hansen, 1913)). The latter was not dissected by Kudinova-Pasternak because it was assigned to a known species and, most likely, it was kept intact at the Zoological Museum of Moscow State Lomonosov University within the original jar. Indeed, an intact specimen was later found by Błażewicz-Paszkowycz (2007a) during her revision of Typhlotanaidae taxa in a vial labelled "Typhlotanais sandersi n. sp., holotype, Mh 4", and Błażewicz-Paszkowycz (2007a) wrongly considered it as type material of Typhlotanais sandersi Kudinova-Pasternak, 1985. In fact, the undissected specimen corresponded to the second Typhlotanais specimen from station 162, identified initially by Kudinova-Pasternak as Typhlotanais mucronatus Hansen, 1913.
A careful comparison of their morphology, based on the original drawings, bring us to the conclusion that the true Typhlotanais sandersi (holotype) and the specimen referred by Błażewicz-Paszkowycz (2007a) as Typhlamia sandersi (Kudinova-Pasternak, 1985) represent two distinct taxa. All species of Typhlamia present an elongated third antennular article with particularly long distal setae (Fig. 1C), and the intact specimen is undoubtedly close to Ty. mucronatus Hansen, 1913; see Błażewicz-Paszkowycz, 2007a: 90-93). The absence of this antennular feature in the holotype of Typhlotanais sandersi illustrated by Kudinova-Pasternak (1985: page 54) drew our attention first, and further analysis revealed other significant differences in the uropods (exopod unarticulated and about half the endopod length in Typhlamia (Fig. 2G), whereas it is clearly biarticulated and subequal to endopod in the holotype) and cheliped carpus or pereonite-1 setation, among other features (see Table 1). The morphological revision of 'long-bodied' typhlotanaids with rounded pereonites revealed that Typhlotanais sandersi Kudinova-Pasternak, 1985 is morphologically close to Typhlotanais angusticheles Kudinova-Pasternak, 1989 and Typhlotanais sp. A (Błażewicz-Paszkowycz et al., 2014) (Table 3). Those three species most likely belong to a new, undescribed, genus, because they are apparently different from both Typhlamia and Typhlotanais aequiremis Lilljeborg, 1864 (type species of Typhlotanais). The combination of features such as the long body and round pereonites distinguishes these three species from other Typhlotanaidae genera. Indeed, the molecular comparison of species of Typhlamia genesis and Typhlotanais sp. A (morphologically close to Ty. sandersi) confirmed that both taxa belong to genetically distinct clades (Fig. 3), giving further support for the establishment of a new genus, herein named Lannisterella n. gen. Of the 'long-bodied' Typhlotanaidae with a developed clinging apparatus on pereopods 4-6 previously known, only a few taxa have rounded pereonite margins. These include the three genera-Torquella, Pulcherella and Typhlamia, and two Typhlotanais species which have very conservative mouth parts, but share several unique morphological characters-Ty. variabilis Hansen, 1913 andTy. incognitus Larsen, Błażewicz-Paszkowycz &Cunha, 2006 ('variabilis' morpho-group) (Hansen, 1913;Larsen, Błażewicz-Paszkowycz & Cunha, 2006). The morphological features that allow these genera and species-group to be distinguished from Lannisterella n. gen. are summarized in Table 1, and Figs. 1, 2 and 4.
Remarks: Lannisterella angusticheles is distinguished from other members of the genus Lannisterella by having cheliped carpus 2.1 L:W (2.7 L:W in L. sandersi and 2.6 L:W in L. cerseiae). Pereopod-1 with three dorsodistal setae in L. angusticheles, two and one respectively in L. sandersi and L. cerseiae.
Swimming male: The description supported with drawings of body habitus and appendages was presented in paper by Błażewicz-Paszkowycz et al. (2014): 443-449.

Remarks:
The 'variabilis' group is proposed for 'long-bodied' of Typhlotanaidae with prickly tubercles and rounded pereonite lateral margins (Table 1). At first glance, the 'variabilis' group may resemble Lannisterella, which also has slender cheliped carpus with 'third' seta and biarticulated uropod rami, and pereonites 1-3 clearly separated by flexible articulations. By this characters, antennule without distal spur, pereonite-1 without lateral seta and pereopods 4-6 carpus with prickly tubercles not surrounded by blunt spines, the members of the morpho-group are distinguished from Lannisterella, which have antennule with distal spur, pereonite-1 with lateral seta and pereopods 4-6 carpus with prickly tubercles surrounded by blunt spines. The first article of the antennule is also less setose, being supplied with fine medial and distal setae, where Lannisterella has four long setae at this article margin.
Currently two species are included within the 'variabilis' morpho-group. Both species can be distinguished by length of the dorsodistal seta in pereopods 4-5 propodus, which is long in Ty. variabilis (reaches tip of unguis) and short (reaches half of the dactylus) in Ty. incognitus.
Currently Typhlotanais sensu stricto includes only the species of the genus (Ty. aequiremis). The 'variabilis' group can be included in Typhlotanais sensu lato. It is recognised that continued research may in the future provide the basis for the establishment of a new genus Identification key for neuters of 'long-bodied' typhlotanaids with rounded pereonites

DISCUSSION
The paradigm that the deep-sea ecosystem is continuous (no topographic barriers) and stable over time resulted in the widespread acceptance of large geographic ranges for deep sea taxa (Kudinova-Pasternak, 1970, 1973Sieg, 1986b). Nevertheless, a new concept of the deep sea as a highly diverse ecosystem has emerged (Zardus et al., 2006;Etter & Bower, 2015), acknowledging that restricted gene flow and population connectivity might redefine the general idea of widely distributed deep-sea species, particularly among Peracarida (Brandt et al., 2012;Hilário et al., 2015;Jakiel, Stępie n & Błażewicz, 2018;Jakiel, Palero & Błażewicz, 2019. The consequences of insufficient knowledge about typhlotanaid taxonomy or inaccurate research methods only become obvious after state-of-the-art methods (e.g., application molecular approach or powerful microscopy) are improved and the data is re-analyzed. Our revision of 'long-bodied' typhlotanaids with rounded pereonites showed Kudinova-Pasternak (1985) was not able to notice the fine morphological features that differentiate Typhlamia mucronata (Hansen, 1913) (Typhlotanais mucronatus in Kudinova-Pasternak, 1985) from earlier studied Typhlamia genesis (see synonyms this article) despite both taxa occupy different oceanic basins. Historical collections, which include type material or hold rare specimens from pioneering scientific expeditions exploring the ocean floor (Beddard, 1886;Hansen, 1913) are kept in museums and treated as most valuable objects (Frutos et al., 2022). Because of their rarity, newly discovered deep-sea species are not always described at once, but they are generally drawn or photographed and described without providing a name, waiting for more material to be compared and supporting the erection of a new taxon (Błażewicz-Paszkowycz & Larsen, 2005;Kavanagh, Frutos & Sorbe, 2015;Stępie n et al., 2022). Such is the case of Typhlotanais sp. A from Błażewicz-Paszkowycz et al. (2014), which was illustrated, diagnosed, and kept unnamed until more material or new evidence could support the erection of a new species. Morphological revision of 'long-bodied' typhlotanaids with rounded pereonites, combined with newly obtained molecular data, allowed us to describe it here as Lannisterella cerseiae n. gen., n. sp. New, overlooked, or mislabelled taxa can be discovered while working with historical collections. Some species are described only provisionally, waiting for a subsequent revision or the discovery of a sibling species (Corbari, Frutos & Sorbe, 2019;Segadilha, Serejo & Błażewicz, 2019). During revision of high-level taxa and examination of historical collections, re-examination and checking of original labels allow to amend specimen misidentifications and/or to correct the geographical coordinates (Frutos & Sorbe, 2010).
Correct taxonomic identification is a baseline for biological research and the analyses at each level of biological organization (e.g., organism, population, community, ecosystem). Its accuracy determines quality of further analyses, e.g., phylogenetic, biogeographic or ecological, therefore, failure in taxonomic identification may turn in erroneous results and lead to wrong conclusions of next-level analyses (Frutos et al., 2022;Kürzel et al., 2022). An integrative approach combining genetic and morphological data allowed us to reconstruct historical (literature) data for material that has been lost or erroneously reported. Its interpretation in the light of new and improved knowledge also allowed us to propose changes in Typhlotanaidae systematics and clarify several taxonomic uncertainties. A phylogenetic analysis based on morphological traits was attempted. Unfortunately, due to high plasticity and divergence, it was not possible to obtain a tree with acceptable parameters (e.g., Consistency Index, Bremer Support). The molecular analysis of Typhlotanaidae taxa presented here must be taken as a preliminary result that requires further studies, including larger number of genes and taxa. While accelerated climate change and plastics are affecting even the deepest parts of the ocean, an accurate estimation and understanding of the biodiversity in this virtually unknown environment is needed before irreversible changes happen.